Peak shaving and energy management for grid-connected pv systems integrated with battery storage

Reducing CO2 emissions is a necessary subject due to the existing ecological problems. Many alternative energy sources can be used instead of fossil fuels. It is widely believed that solar energy can sustainably replace fossil fuel sources without harming the environment. These days, commercial and residential photovoltaic (PV) systems are extensively coming into the market due to the following advantages: (1) More affordable costs with respect to homeowners’ economic situations and (2) Utilizing the roof of the buildings as the supporting structure, thereby eliminating land and direct structure expenses [1]. However, proper interfaces will need to be provided between these systems and the utility in order to maximize the benefits associated with them. Small battery energy storage systems (BESS) have demonstrated to be effective devices for proper interfacing between residential/commercial/industrial PV systems and utilities in order to provide uninterrupted and reliable power to the loads. This project focuses on the application of BESS in PV systems as the continuation of previous works based on 1) a state-space based battery energy storage system; [2], and 2) a simple and effective approach for peak load shaving using battery energy storage systems.[3] The grid-connected PV system with batteries (PV+BESS) containing DC/DC converter, AC/DC inverter, AC loads and BESS, is capable of simultaneous control of active power, reactive power, and DC link voltage. Continuing on the previous work, this project has proposed and verified a control strategy based on state-space model(s) of PV+BESS by utilizing an energy management strategy with the goal of peak-shaving, while considering batteries’ degradation and ageing limits. Simulations have been performed in different battery capacity cases and the results have been compared with the simple approach described in [3]. The simulation is performed using Simulink/SimPowerSystems toolbox under Matlab, and the models are created based on several published research papers. PV+BESS control strategy was analyzed, and the results were simulated and verified in two different examples.